2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
19 #ifndef POSITION_H_INCLUDED
20 #define POSITION_H_INCLUDED
29 #include "nnue/nnue_accumulator.h"
34 // StateInfo struct stores information needed to restore a Position object to
35 // its previous state when we retract a move. Whenever a move is made on the
36 // board (by calling Position::do_move), a StateInfo object must be passed.
40 // Copied when making a move
43 Value nonPawnMaterial[COLOR_NB];
49 // Not copied when making a move (will be recomputed anyhow)
53 Bitboard blockersForKing[COLOR_NB];
54 Bitboard pinners[COLOR_NB];
55 Bitboard checkSquares[PIECE_TYPE_NB];
60 Eval::NNUE::Accumulator accumulator;
61 DirtyPiece dirtyPiece;
65 // A list to keep track of the position states along the setup moves (from the
66 // start position to the position just before the search starts). Needed by
67 // 'draw by repetition' detection. Use a std::deque because pointers to
68 // elements are not invalidated upon list resizing.
69 using StateListPtr = std::unique_ptr<std::deque<StateInfo>>;
72 // Position class stores information regarding the board representation as
73 // pieces, side to move, hash keys, castling info, etc. Important methods are
74 // do_move() and undo_move(), used by the search to update node info when
75 // traversing the search tree.
83 Position(const Position&) = delete;
84 Position& operator=(const Position&) = delete;
86 // FEN string input/output
87 Position& set(const std::string& fenStr, bool isChess960, StateInfo* si, Thread* th);
88 Position& set(const std::string& code, Color c, StateInfo* si);
89 std::string fen() const;
91 // Position representation
92 Bitboard pieces(PieceType pt = ALL_PIECES) const;
93 template<typename... PieceTypes>
94 Bitboard pieces(PieceType pt, PieceTypes... pts) const;
95 Bitboard pieces(Color c) const;
96 template<typename... PieceTypes>
97 Bitboard pieces(Color c, PieceTypes... pts) const;
98 Piece piece_on(Square s) const;
99 Square ep_square() const;
100 bool empty(Square s) const;
101 template<PieceType Pt>
102 int count(Color c) const;
103 template<PieceType Pt>
105 template<PieceType Pt>
106 Square square(Color c) const;
109 CastlingRights castling_rights(Color c) const;
110 bool can_castle(CastlingRights cr) const;
111 bool castling_impeded(CastlingRights cr) const;
112 Square castling_rook_square(CastlingRights cr) const;
115 Bitboard checkers() const;
116 Bitboard blockers_for_king(Color c) const;
117 Bitboard check_squares(PieceType pt) const;
118 Bitboard pinners(Color c) const;
120 // Attacks to/from a given square
121 Bitboard attackers_to(Square s) const;
122 Bitboard attackers_to(Square s, Bitboard occupied) const;
123 void update_slider_blockers(Color c) const;
124 template<PieceType Pt>
125 Bitboard attacks_by(Color c) const;
127 // Properties of moves
128 bool legal(Move m) const;
129 bool pseudo_legal(const Move m) const;
130 bool capture(Move m) const;
131 bool capture_stage(Move m) const;
132 bool gives_check(Move m) const;
133 Piece moved_piece(Move m) const;
134 Piece captured_piece() const;
136 // Doing and undoing moves
137 void do_move(Move m, StateInfo& newSt);
138 void do_move(Move m, StateInfo& newSt, bool givesCheck);
139 void undo_move(Move m);
140 void do_null_move(StateInfo& newSt);
141 void undo_null_move();
143 // Static Exchange Evaluation
144 bool see_ge(Move m, Value threshold = VALUE_ZERO) const;
146 // Accessing hash keys
148 Key key_after(Move m) const;
149 Key material_key() const;
150 Key pawn_key() const;
152 // Other properties of the position
153 Color side_to_move() const;
154 int game_ply() const;
155 bool is_chess960() const;
156 Thread* this_thread() const;
157 bool is_draw(int ply) const;
158 bool has_game_cycle(int ply) const;
159 bool has_repeated() const;
160 int rule50_count() const;
161 Value non_pawn_material(Color c) const;
162 Value non_pawn_material() const;
164 // Position consistency check, for debugging
165 bool pos_is_ok() const;
169 StateInfo* state() const;
171 void put_piece(Piece pc, Square s);
172 void remove_piece(Square s);
175 // Initialization helpers (used while setting up a position)
176 void set_castling_right(Color c, Square rfrom);
177 void set_state() const;
178 void set_check_info() const;
181 void move_piece(Square from, Square to);
183 void do_castling(Color us, Square from, Square& to, Square& rfrom, Square& rto);
184 template<bool AfterMove>
185 Key adjust_key50(Key k) const;
188 Piece board[SQUARE_NB];
189 Bitboard byTypeBB[PIECE_TYPE_NB];
190 Bitboard byColorBB[COLOR_NB];
191 int pieceCount[PIECE_NB];
192 int castlingRightsMask[SQUARE_NB];
193 Square castlingRookSquare[CASTLING_RIGHT_NB];
194 Bitboard castlingPath[CASTLING_RIGHT_NB];
202 std::ostream& operator<<(std::ostream& os, const Position& pos);
204 inline Color Position::side_to_move() const { return sideToMove; }
206 inline Piece Position::piece_on(Square s) const {
211 inline bool Position::empty(Square s) const { return piece_on(s) == NO_PIECE; }
213 inline Piece Position::moved_piece(Move m) const { return piece_on(from_sq(m)); }
215 inline Bitboard Position::pieces(PieceType pt) const { return byTypeBB[pt]; }
217 template<typename... PieceTypes>
218 inline Bitboard Position::pieces(PieceType pt, PieceTypes... pts) const {
219 return pieces(pt) | pieces(pts...);
222 inline Bitboard Position::pieces(Color c) const { return byColorBB[c]; }
224 template<typename... PieceTypes>
225 inline Bitboard Position::pieces(Color c, PieceTypes... pts) const {
226 return pieces(c) & pieces(pts...);
229 template<PieceType Pt>
230 inline int Position::count(Color c) const {
231 return pieceCount[make_piece(c, Pt)];
234 template<PieceType Pt>
235 inline int Position::count() const {
236 return count<Pt>(WHITE) + count<Pt>(BLACK);
239 template<PieceType Pt>
240 inline Square Position::square(Color c) const {
241 assert(count<Pt>(c) == 1);
242 return lsb(pieces(c, Pt));
245 inline Square Position::ep_square() const { return st->epSquare; }
247 inline bool Position::can_castle(CastlingRights cr) const { return st->castlingRights & cr; }
249 inline CastlingRights Position::castling_rights(Color c) const {
250 return c & CastlingRights(st->castlingRights);
253 inline bool Position::castling_impeded(CastlingRights cr) const {
254 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
256 return pieces() & castlingPath[cr];
259 inline Square Position::castling_rook_square(CastlingRights cr) const {
260 assert(cr == WHITE_OO || cr == WHITE_OOO || cr == BLACK_OO || cr == BLACK_OOO);
262 return castlingRookSquare[cr];
265 inline Bitboard Position::attackers_to(Square s) const { return attackers_to(s, pieces()); }
267 template<PieceType Pt>
268 inline Bitboard Position::attacks_by(Color c) const {
270 if constexpr (Pt == PAWN)
271 return c == WHITE ? pawn_attacks_bb<WHITE>(pieces(WHITE, PAWN))
272 : pawn_attacks_bb<BLACK>(pieces(BLACK, PAWN));
275 Bitboard threats = 0;
276 Bitboard attackers = pieces(c, Pt);
278 threats |= attacks_bb<Pt>(pop_lsb(attackers), pieces());
283 inline Bitboard Position::checkers() const { return st->checkersBB; }
285 inline Bitboard Position::blockers_for_king(Color c) const { return st->blockersForKing[c]; }
287 inline Bitboard Position::pinners(Color c) const { return st->pinners[c]; }
289 inline Bitboard Position::check_squares(PieceType pt) const { return st->checkSquares[pt]; }
291 inline Key Position::key() const { return adjust_key50<false>(st->key); }
293 template<bool AfterMove>
294 inline Key Position::adjust_key50(Key k) const {
295 return st->rule50 < 14 - AfterMove ? k : k ^ make_key((st->rule50 - (14 - AfterMove)) / 8);
298 inline Key Position::pawn_key() const { return st->pawnKey; }
300 inline Key Position::material_key() const { return st->materialKey; }
302 inline Value Position::non_pawn_material(Color c) const { return st->nonPawnMaterial[c]; }
304 inline Value Position::non_pawn_material() const {
305 return non_pawn_material(WHITE) + non_pawn_material(BLACK);
308 inline int Position::game_ply() const { return gamePly; }
310 inline int Position::rule50_count() const { return st->rule50; }
312 inline bool Position::is_chess960() const { return chess960; }
314 inline bool Position::capture(Move m) const {
316 return (!empty(to_sq(m)) && type_of(m) != CASTLING) || type_of(m) == EN_PASSANT;
319 // Returns true if a move is generated from the capture stage, having also
320 // queen promotions covered, i.e. consistency with the capture stage move generation
321 // is needed to avoid the generation of duplicate moves.
322 inline bool Position::capture_stage(Move m) const {
324 return capture(m) || promotion_type(m) == QUEEN;
327 inline Piece Position::captured_piece() const { return st->capturedPiece; }
329 inline Thread* Position::this_thread() const { return thisThread; }
331 inline void Position::put_piece(Piece pc, Square s) {
334 byTypeBB[ALL_PIECES] |= byTypeBB[type_of(pc)] |= s;
335 byColorBB[color_of(pc)] |= s;
337 pieceCount[make_piece(color_of(pc), ALL_PIECES)]++;
340 inline void Position::remove_piece(Square s) {
343 byTypeBB[ALL_PIECES] ^= s;
344 byTypeBB[type_of(pc)] ^= s;
345 byColorBB[color_of(pc)] ^= s;
348 pieceCount[make_piece(color_of(pc), ALL_PIECES)]--;
351 inline void Position::move_piece(Square from, Square to) {
353 Piece pc = board[from];
354 Bitboard fromTo = from | to;
355 byTypeBB[ALL_PIECES] ^= fromTo;
356 byTypeBB[type_of(pc)] ^= fromTo;
357 byColorBB[color_of(pc)] ^= fromTo;
358 board[from] = NO_PIECE;
362 inline void Position::do_move(Move m, StateInfo& newSt) { do_move(m, newSt, gives_check(m)); }
364 inline StateInfo* Position::state() const { return st; }
366 } // namespace Stockfish
368 #endif // #ifndef POSITION_H_INCLUDED